I have been watching several groups / harems of chickens. Some are free range and some are in breeding pens. I have been noticing with caged birds the rooster places himself in locations the hen will ultimately lay in and carries on with a vocalization that he makes only then. He seems to do this only once per hen per breeding effort. The hen more often than not then lays eggs in that location starting that or following day and proceeds to lay entire clutch over following days. Rooster does not enter nest again. Somehow rooster knows when hen is getting ready to lay first egg of a clutch. Another thing observed with free ranging group is that if eggs in a nest to do not belong to harem, then rooster destroys clutch by rolling them out and away from nest. If broken during process he and hen with him consume contents. This occurs even with free-range birds nest under log in field. Rooster also appears to know which clutches belong to his group based on this.